4.33 Million BTC in Reused Addresses — A Future Security Challenge?
Bitcoin’s security is back in the spotlight, but this time the discussion is about something that could matter years down the road: quantum computing.
According to Glassnode data reported on October 8, around 4.33 million BTC are held in reused addresses, representing approximately 21.5% of circulating supply. When older address types are included, the total amount of BTC with publicly exposed keys rises to roughly 6.26 million BTC.
So, why does this matter?
When Bitcoin addresses are reused after a transaction reveals their public keys, the keys can remain visible on the blockchain. A sufficiently powerful quantum computer could theoretically use exposed public keys to threaten the security of those funds.
But there’s an important distinction: public-key exposure does not mean those Bitcoin can be stolen today. No practical quantum attack capable of breaking Bitcoin’s cryptography at this scale has been demonstrated.
The bigger issue is preparation.
As quantum technology advances, Bitcoin developers, exchanges and wallet providers may need to consider stronger post-quantum protections and ways to migrate funds safely.
For now, this is a long-term security challenge, not a reason to panic.
Bitcoin’s next major security milestone may be about preparing for the future before the threat becomes real.
